1. Field
The present disclosure relates generally to methods and apparatus for Universal Serial Bus (USB) connection sharing in a multi-processor or multi-chip device, and more specifically to selectively sharing a USB connection in a multi-processor or multi-chip device based on whether or not concurrent tethered high-speed network access technology networking and USB data transfer is occurring in the device.
2. Background
Integrating a standalone modem chip, such as an LTE modem chip, with an Application Processor in a communication device Multi-processor USB device such as a smart phone introduces a problem of sharing a USB connection to a personal computer (PC) or a peripheral device. A challenging scenario is when the phone is connected to a PC or peripheral device over USB while also providing tethered networking (e.g., Long Term Evolution (LTE)) USB connectivity in parallel to transfer large multimedia files, as one example, between the PC and the phone on the same USB connector. Since technologies such as LTE or Wi-Fi, for example, enable very high data rates (up to 326.4 Mbit/s on the downlink and up to 86.5 Mbit/s on the uplink), it becomes challenging to route this data stream through the Application Processor.
It is noted that it is known to solve similar problems for lower speed networks by routing all IP traffic from the modem chip to the Application Processor and then forwarding it to the PC or peripheral device via USB, where the Application Processor is connected directly to the USB port or connector of a device. Such designs, however, do not scale well as network data rates go up, such as in LTE systems. In such a case, an Application Processor's performance is consequently limited or diminished especially when there are concurrency requirements for the Application Processor and the modem chip providing network connectivity (or even other chips in the device requiring USB connectivity to the USB port).
Other systems may share a single USB port for connection to the PC and switch the connection to either a modem processor or an application processor based on the desired use case. In one example, such designs may require that LTE tethered networking to the PC and multimedia content transfer to the phone are mutually exclusive. Accordingly, there is a need for improved USB connectivity in multi-processor or multi-chip devices where more than one processor or chip requires external USB communications, particularly for high data rate devices such as LTE devices.